This invention relates to a water jet propulsion unit and more particularly to an improved driving arrangement for a jet propulsion unit that facilitates servicing.
A popular form of watercraft is powered by a jet propulsion unit that includes a housing that defines an inlet, a pumping cavity and a discharge outlet. An impeller is rotatably journaled within the pumping cavity for drawing water from the inlet and discharging it through the outlet so as to propel the associated watercraft. This type of propulsion unit is normally mounted in a recess formed in the underside of the watercraft hull and rearwardly of the engine compartment. In normal practice, the impeller is driven by an impeller shaft that extends forwardly and which is coupled to a drive shaft driven by the engine which is contained within the engine compartment.
Frequently, the jet propulsion unit must be serviced. For example, the impeller may become damaged when foreign objects are drawn through the jet propulsion unit and, with the prior art type of constructions, it has been necessary to remove the engine from the watercraft so as to permit sufficient axial movement of the respective shafts so that the jet propulsion unit can be removed and serviced. Although splined connections have been employed between the drive shaft and the impeller shaft, the prior art type of construction have located these splined connections in the area of the hub of the impeller. As a result, it is necessary to remove the engine and to move it forwardly so as to permit the removal of the jet propulsion unit. In addition to this difficulty, the location of the splined connection at the hub of the impeller means that the hub of the impeller must be made sufficiently large so as to transmit the driving thrust without breakage. However, as the size of the hub of the impeller is increased, the efficiency of the jet propulsion unit is accordingly decreased.
It is, therefore, a principal object of this invention to provide an improved jet propulsion unit for a watercraft.
It is a further object of this invention to provide a jet propulsion unit for watercraft that can be conveniently serviced without necessitating removal of the engine from the watercraft.
It is a further object of this invention to provide an improved driving connection between the drive shaft and impeller shaft of the jet propelled watercraft so as to facilitate servicing.
It is a further object of this invention to provide an improved driving connection for a jet propulsion unit of a watercraft that will not increase the size of the impeller hub.